Filters For Smoking Articles For Less Additive(s) Loss

ABSTRACT

Improvements are provided in filters for use in smoking articles, including the use of randomly oriented discrete fibres. The improvements mainly relate to the loss of additive(s) in said filters and to the manufacture thereof. In one embodiment, a filter for a smoking article includes randomly oriented discrete fibres and at least one particulate additive, the at least one particulate additive being dispersed within the filter, wherein a value obtained by dividing a volume fraction of the at least one particulate additive by a volume fraction of the fibres is less than about 1100%.

FIELD OF THE INVENTION

The present invention relates to improvements in filters for use in smoking articles, comprising randomly oriented discrete fibres. The improvements mainly relate to the loss of additive(s) in said filters and to the manufacture thereof.

BACKGROUND TO THE INVENTION

In conventional filter cigarettes, the filter commonly consists of a single segment of filtration material, typically a continuous tow of filamentary cellulose acetate plasticised with triacetin, circumscribed by porous and/or non-porous plug wrap. The cellulose acetate is gathered together to form a rod which is cut to form individual filter segments. The filter for a smoking article may be made of one segment of filter rod, or may be made from multiple segments.

In the past it has been proposed to replace the continuous tow with randomly oriented discrete fibres of cellulose acetate. The advantages of using such kind of fibres have been reported and listed in several publications, like WO 2009/080368, WO 2009/093051, WO 2013/068337, WO 2013/164624 and WO 2013/164623. Filter manufacturing machines specifically developed for making such kind of filters are also known, e.g. Turmalin machine made by Hauni Maschinenbau AG, Germany.

With randomly oriented discrete fibres, filters having higher additive loadings can be produced compared to filters using continuous tow. In addition to this, the Turmalin machine is reported as allowing said higher loadings without using any plasticizer such as triacetin, e.g. in WO 2013/164624 and WO 2013/164623.

However, all publications are silent on how to process filters having said higher additive loading. Indeed, the present inventors have found that as soon as filters comprising randomly oriented discrete fibres and high additive loading are cut in order to form individual filter segments or to be assembled in multiple segments filters, a very significant amount of the additive is lost.

Therefore, there is a need to provide filters comprising randomly oriented discrete fibres and a stable, long lasting high additive loading with good performance of the additive, as well as smoking articles with these filters.

SUMMARY OF THE INVENTION

The inventors identified particulate additive, e.g. granule, loss during the combining process as a problem in terms of filter quality and machinability for the usage of granulated filters with high loadings of additives like granules and randomly oriented fibres, e.g. randomly oriented acetate (ROA) fibres. With regard to filter quality, pressure drop in the filter and filter burst are significantly affected by granule loss.

An exemplary filter has a circumference of 23.9 mm and a filter length of 120 mm, and contains 2.2 mg/mm filter tow. 13 mg/mm of charcoal granules are added as additive. This results in a target pressure drop (PD) of 318 mmWG/rod (mm water gauge/rod; 3118 Pa/rod).

A 10 wt. % granule loss in the above exemplary filter results in a pressure drop of 287 mmWG/rod, resulting in a 10% pressure drop loss compared to the target pressure drop. This is not acceptable with regard to cigarette design.

Similarly, a 5 wt. % granule loss results in a pressure drop of 303 mmWG/rod, resulting in 5% PD loss. This could for example be seen as an upper limit with regard to cigarette design/quality.

In addition, loose granules can accumulate at the seam of the combiner plug wrap used to attach a plurality of filter segments. This may even prevent seam formation as the loose granules reduce the effective area for the adhesive that is typically applied to form the seam. As a result, the filter may burst open. The inventors have identified that this problem increases with increased loss of granules.

Furthermore, having regard to machinability, charcoal contamination around the machine is a problem that can lead to machine stoppage. To mitigate this problem special protections have been installed to ensure that charcoal does not accumulate in problematic areas, such as the plug wrap gluing and guiding system, and frequent machine cleaning is necessary.

Therefore, a target for additive loss, e.g. granule loss, should be for example less than about 5%, based on the total weight of the additive, to keep a good filter quality and machinability.

The inventors found that an improvement in additive loss, i.e. decreased loss of at least one particulate additive, can be achieved by a filter for a smoking article comprising a certain amount of fibres and a certain amount of additive.

Thus, a first aspect of the invention provides a filter for a smoking article comprising randomly oriented discrete fibres and at least one particulate additive, the additive being dispersed within the filter, wherein the value obtained by dividing the volume fraction of the additive (cc/mm) by the volume fraction of the fibres (cc/mm) is less than about 1100%.

Furthermore, the invention relates to a smoking article comprising the filter of the present invention.

Further preferred and exemplary embodiments of the invention are indicated in the dependent claims and the following detailed description, which, however, do not restrict the scope of the invention and only help to understand and explain the features of the present invention. Deviations and modifications on these particular features, particular in regard to other aspects of the invention, can be made without departing from the scope of the invention.

DESCRIPTION OF FIGURES

The invention will be further described in detail in the following with reference to the figures and particular embodiments thereof, without being limited thereto.

In the figures the following is shown:

FIG. 1 shows a graph of exemplary data taken from the Examples.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

All ranges disclosed herein are to be considered to be supplemented by the term “about”, unless clearly defined to the contrary or otherwise clear from the context.

All numbers or percentages relating to amounts of a substance within this application are given in wt. %, unless clearly defined to the contrary or otherwise clear from the context.

The term “randomly oriented discrete fibres” refers to a plurality of fibres that can be distinguished from each other and are physically separated, i.e. discrete fibres. They are randomly oriented in three directions, i.e. form a random 3-dimensional fibre network wherein the fibres are directed in any direction, without all fibres being directed in the same direction. The fibres can have different lengths or have the same lengths as well as the same diameter or different diameters, and can be uniform or non-uniform with regard to their individual sizes and shapes.

The term “smoking article” relates to all kinds of smokable products like cigarettes, cigars, cigarillos, etc. In these smoking articles, the kind of smokable material used, e.g. tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco, tobacco substitutes, non-burnable products, etc., as well as mixtures thereof, is not particularly limited. These smoking articles are provided with a filter according to the invention.

Smoking articles and their formats can be e.g. characterized according to the cigarette length, with “regular” being in the range 68-75 mm, e.g. from about 68 mm to about 72 mm, “short” or “mini” being 68 mm or less, “king-size” being in the range 75-91 mm, e.g. from about 79 mm to about 88 mm, “long” or “super-king” being in the range 91-105 mm, e.g. from about 94 mm to about 101 mm, and “ultra-long” being in the range from about 110 mm to about 121 mm.

They can also be characterized by the circumference of the smoking article, e.g. a cigarette, with “regular” having a circumference of about 23-25 mm, “wide” having a circumference of greater than 25 mm, “slim” having a circumference of about 22-23 mm, “demi-slim” having a circumference of about 19-22 mm, “super-slim” having a circumference of about 16-19 mm, and “micro-slim” having a circumference of less than about 16 mm.

Accordingly, a cigarette in a king-size, super-slim format will, for example, have a length of about 83 mm and a circumference of about 17 mm. Cigarettes in the regular, king-size format have e.g. a circumference of from 23 to 25 mm and an overall length of from 75 to 91 mm.

Each format may be produced with filters of different lengths, smaller filters being generally used in formats of smaller lengths and circumferences. Typically the filter length will be from 15 mm to 30 mm. The tipping paper can have a greater length than the filter, for example from 3 to 10 mm longer.

A particulate additive is an additive that is present in the form of particles, i.e. particularly in solid form. The particulate additive(s) can be e.g. in powder (particle diameter of about 50 to 150 μm) and/or granular form (particle diameter of about 150 to 1000 μm).

According to one aspect, the present invention relates to a filter for a smoking article comprising randomly oriented discrete fibres and at least one particulate additive, the (particulate) additive being dispersed within the filter, wherein the value obtained by dividing the volume fraction of the (particulate) additive(s) (cc/mm) by the volume fraction of the fibres (cc/mm) is less than about 1100%, for example less than about 1000%, such as less than about 900%, e.g. less than about 800%.

The volume fraction herein is the ratio of a volume of a certain material, e.g. the particulate additive and/or the randomly oriented discrete fibres, to the total available volume in the filter. The volume of a certain material can thereby be calculated using the bulk density of the material and the weight thereof. The total volume of a filter can be determined by consideration of the shape of the filter, e.g.—in case of a cylindrical filter—using the diameter and length. Suitable measurement procedures for the bulk density of the particulate additive are known from ASTM D2854-2009 for granular activated carbon, ASTM D1895 test method A for fine granules and powders that can be poured readily through a small funnel (e.g. silica granule, hydrotalcite, paper granule, acetate flake, or coffee granule), ASTM D1895 test method B for coarse granular materials, including dice and pellets, that either cannot be poured or that are poured with difficulty through the funnel described in ASTM D1895 test method A (e.g. tobacco granule, sugar granule), and ASTM D1895 test method C for materials supplied in the form of coarse flakes, chips, cut fibres, or strands (e.g. mint leaf, tobacco leaf). A suitable measurement procedure for the bulk density of the randomly oriented discrete fibres is known from ASTM D3887-1995.

By keeping a certain ratio between the volume fraction of the additive(s) and the volume fraction of the fibres, it is possible to minimize the loss of additive, e.g. resulting from cutting during preparation of the filters, e.g. cutting the filters to a certain desired length of e.g. 3 to 20 mm, e.g. 6 to 12 mm, or e.g. 8 to 10 mm. Individual filter segments, or segments for multiple segments filters, can be formed by cutting. According to certain embodiments, the loss weight of the additive(s)—particularly during cutting—is less than 5%, e.g. less than 4.5%, e.g. less than 4%, e.g. less than 3%, based on the total weight of the additive(s). The weight loss can be determined by weighing using usual procedures. One example is to determine the weight difference between the weight of a certain filter before cutting and the total combined weight of cut filter segments—cut from this filter—after cutting. Especially, according to certain embodiments, it should be ensured that no loss is obtained due to cutting in any other components of the filter, e.g. the randomly oriented discrete fibres and/or a wrapping material, which can be ensured by collecting losses of such other components, if occurring, weighing them and adding this weight to the combined weight of the cut filter segments, before this total combined weight is subtracted from the weight of the filter before cutting. According to certain embodiments, loss of other components, e.g. filter tows, during cutting is negligible. According to certain embodiments, the loss of additive is substantially due to the at least one particulate additive, e.g. due to the at least one particulate additive.

Thus, the present invention also relates to a process of producing a filter for a smoking article according to the present invention, as described below.

The dispersion of the at least one particulate additive in the filter is not particularly limited and can be in any form. It can for example be a homogeneous or heterogeneous dispersion within the filter, e.g. the randomly oriented discrete fibres, and/or also at other locations between the randomly oriented discrete fibres and another material, e.g. a filter wrapping material.

The filter of the invention can contain one or more particulate additive(s) which are not particularly limited and can be those particulate additives normally used in filters for smoking articles. Examples of suitable particulate additives include flavourants or sorbents—e.g. activated carbon/charcoal, zeolite, ion exchange resin, magnesium silicate like sepiolite, silica gel, alumina, molecular sieves, carbonaceous polymer resins and diatomaceous earths, or combinations thereof. Also, other additives, such as humectants, can be used. According to certain aspects, the particulate additive comprises or is charcoal/activated carbon. According to certain embodiments, the at least one particulate additive has a particle size from 50 to 2000 μm, e.g. from 100 to 1000 μm, as determined e.g. using sieve analysis.

The material of the randomly oriented discrete fibres, which can be comprised in or be the filter tow material, is not particularly limited and can include a material that is typically used in filters for smoking articles, e.g. cigarette filters. It can include natural fibre materials which can be e.g. produced from cellulose, herb materials like tobacco, or synthetic materials like polypropylene. For example, the material of the randomly oriented discrete fibres can comprise or be cellulose acetate or polypropylene. Also mixtures of two or more fibre materials are possible. According to certain aspects, the filter tow material may have a filament denier in the range of from 3.0 up to 12.0 D, e.g. of between 4.0 and 10.0 D, e.g. of between 5.0 and 8.0 D, e.g. of about 6.0 D.

According to certain embodiments, the range of the combined loading amount of the additive and the fibre is between 2.4 mg/mm and 19 mg/mm for a filter of any diameter, e.g. having a diameter between the lower limit for a super-slim size and the upper limit of a regular size, i.e. between 16 and 25 mm. According to certain embodiments, the range of the combined loading amount of the additive and the fibre is between 3 mg/mm and 18 mg/mm, e.g. between 8 mg/mm and 17 mg/mm. According to certain embodiments, the range of the combined loading amount of the additive and the fibre is between 8 mg/mm and 17 mg/mm, particularly for a regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm. According to further embodiments, the range of the combined loading amount of the additive and the fibres is 9 mg/mm to 16 mg/mm, e.g. 10 mg/mm to 14.5 mg/mm, e.g. 10.5 mg/mm to 14 mg/mm, e.g. 11 mg/mm to 13 mg/mm, particularly for a regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.

According to certain embodiments, the amount of the additive is between 1 mg/mm and 13.5 mg/mm for a filter of any diameter, e.g. having a diameter between the lower limit for a super-slim size and the upper limit of a regular size, i.e. between 16 and 25 mm. According to certain embodiments, the amount of the additive is between 6 mg/mm and 13 mg/mm. According to certain embodiments, the amount of the additive is in the range between 7 mg/mm and 12 mg/mm, e.g. in the range between 7.5 mg/mm and 11 mg/mm, e.g. in the range of from 8 mg/mm up to 10 mg/mm, particularly for a regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.

According to certain embodiments, the amount of fibres is between 1.4 and 5.5 mg/mm for a filter of any diameter, e.g. having a diameter between the lower limit for a super-slim size and the upper limit of a regular size, i.e. between 16 and 25 mm. According to certain embodiments, the amount of fibres is between 2.0 and 4.5 mg/mm, e.g. between 2.0 and 4.0 mg/mm, e.g. between 2.2 mg/mm and 3.8 mg/mm, e.g. between greater than 2.2 mg/mm and up to 3.7 mg/mm. According to certain embodiments, the fibre loading amount is in the range of from 2.5 mg/mm to 3.6 mg/mm, e.g. from 2.8 mg/mm to less than 3.6 mg/mm, e.g. in the range from 3.0 mg/mm up to 3.5 mg/mm, particularly for a regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.

According to certain embodiments, the amount of the additive is between 6 mg/mm and 13 mg/mm, and/or the amount of fibres is between 2.0 and 4.0 mg/mm, e.g. between 2.2 mg/mm and 3.8 mg/mm, e.g. between greater than 2.2 mg/mm and up to 3.7 mg/mm, particularly for a regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.

The filter of the invention can have any shape and is not particularly limited, but is preferably in a shape commonly used in smoking articles, e.g. in cylindrical shape. According to certain embodiments, the filter has a cylindrical shape with a circumference of the cylinder being equal to or smaller than 26 mm, preferably equal to or smaller than 23.9 mm.

Further, the filter of the invention may optionally include other materials, for example one or more liquid(s) (such as a flavourant, e.g. menthol solution).

In addition, the present filter is also not particularly limited regarding other components of the filter and can include components that are commonly used in filters for smoking articles. For example, the filter may be wrapped with a wrapper or plug wrap, for example a wrapper of paper, e.g. an air-permeable paper. Particulate additives as discussed above can also be applied to the wrapper or plug wrap surrounding the filter material. The material of the plug wrap is not particularly limited and can comprise paper and/or plastic materials like PE, PP, etc.

According to certain embodiments, the filter of the present invention does not contain a binder or a plasticizer, making processing and manufacturing of the filter easier. A binder may have the disadvantage that it solidifies after application, which leads to contamination in the process and a higher pressure drop. A plasticizer like triacetin can, especially at high loading, lead to melt holes in the filter, i.e. dissolve the filter tow, causing defect in the smoking article. Even without using a binder or a plasticizer, additive loss in the present filter can be reduced.

According to certain embodiments, the filter comprising randomly oriented discrete fibres and the additive is cut into desired lengths in order to form individual filter segments or to be assembled to multiple segments filters. In such a case—by determining the weight difference between the filter before and after cutting, resulting from the loss of additive during cutting, e.g. to a length of 6 mm—the loss weight of the additive can be less than about 5%, e.g. less than about 4.5%, e.g. less than about 4%, e.g. less than about 3%, based on the total weight of the additive.

In a further aspect, the present invention relates to a smoking article comprising the filter of the present invention. The smoking article is not particularly limited and can be e.g. a cigarette, a cigar or a cigarillo in any size and shape. In such a smoking article, also two or more of the filters according to the invention can be used, and/or the present filter can be used in combination with another filter, e.g. in a segmented filter. Regarding the further composition, the smoking article of the invention is not limited. As a matter of course, a tobacco containing segment can be contained in the smoking article, wherein the tobacco is not limited, and the smoking article can e.g. be wrapped using usual material, and can also contain other components like a tipping paper.

In a further aspect, the present invention also relates to a method of producing/manufacturing a filter for a smoking article, particularly according to the present invention, wherein at least one particulate additive and randomly oriented fibres are provided and added to a filter for a smoking article, wherein the at least one particulate additive is dispersed in the filter, wherein the value obtained by dividing the volume fraction of the additive (cc/mm) by the volume fraction of the fibres (cc/mm) is less than about 1100%.

The filter of the present invention may be manufactured by known methods, using common equipment, e.g. a Turmalin machine from Hauni, Del. The at least one particulate can be, for example added into the filter tow, i.e. the randomly oriented discrete fibres, and then the tow is shapes into e.g. a rod of any desirable circumference. The e.g. cylindrical rod formed to any desired size and shape may be wrapped in a plug wrap and sealed with an adhesive by means that are well-known in the prior art, e.g. using spiral anchor glue. Afterwards, the filter rod can further be cut into desired lengths using known methods. Other additives, if included, can be introduced at suitable times in the filter production process.

Using the filter of the present invention, a smoking article can be produced, e.g. by combining one or more filters of the invention with a tobacco rod and optionally other filters, and wrapping the resultant, e.g. by methods known in the art.

EXAMPLES

The present invention will now be described with reference to examples thereof, without limiting the scope of the invention to these particular examples.

Example 1

In the following, different filters for cigarettes were produced with different loadings of additive and different loadings and sizes of randomly oriented discrete fibres (hereinafter also referred to as filter tow).

The controllable parameters were herein as follows:

Charcoal loading: 8-13 mg/mm

Filter tow loading: 2.0-3.5 mg/mm

Filter tow cut length: 10-20 mm

Furthermore, the following parameters were given for production. Cylindrical base filters were produced with a circumference of 23.9 mm and a length of 120 mm length, which were then wrapped with a non-porous plug wrap. After wrapping, the base filter was cut 19 times to obtain equal cut filters, each with a final length of 6 mm. For anchor glue application, a spiral glue application was used.

Charcoal was supplied from JacobiCarbons (Sweden). It had a bulk density of 603 kg/m³, a CCl₄ adsorption of 60-70%, and an ASTM Mesh size of 30×60 (595 μm×250 μm). For the present charcoal, the bulk density was determined by ASTM D2854-2009.

Filter tow, i.e. randomly oriented discrete fibres, was obtained from Celanese. It had the following properties: Denier per Filament (g/9000m) was 6.0 D, and total Denier (g/9000 m) was 17000 D, with the cross Section being Y. The bulk density was 1255 kg/m³ measured according to ASTM D3887-1995.

As a plug wrap, a wrap from Delfort with a porosity (cm³/cm²/min) of 0 (i.e. without pores), a basis weight of 27 g/m², and a thickness of 43 μm was used.

Base rod making of base filter rods was carried out with a Turmalin base rod maker, supplied by Hauni, Del., at a machine speed of 200 m/min, to obtain base filter rods/base filters with a length of 120 mm.

These base filters were then introduced into a combining process, using a Solaris (Combiner) from ITM working at a machine speed of 350 m/min.

The following additive loss test has been carried out:

1. Before entering into the combining process, selected base filter rods were separately color-coded by colour application to the outside (using a coloured pen), and weighed.

2. The base filter rods were then introduced into the combining process and processed, wherein the base filter rods were cut from the original length of 120 mm to a target length of 6 mm.

3. After the combining process, the coloured & cut filters, i.e. filter tips, were collected, and cut filters with the same colour, i.e. coming from the same base filter rod, were combined.

4. These combined, cut filter rods were weighed, and the weight was compared to the weight of the base filter rod with the same colour, the weight difference representing loss in the combining process. It was confirmed visually that substantially no other losses but charcoal losses arose in the combining process, and further losses, if occurring, were negligible.

The results for several filters of comparative examples (Comp. Ex.) and examples (Ex.) with different charcoal and filter tow loading and different length of the fibres, after cutting the base filter rods, with regard to additive loss are given in Table 1. Standard deviations (STDEV) were calculated for 15 samples in each example, respectively comparative example, using the Excel function “stdev”.

TABLE 1 Product parameter Additive loss Charcoal Filter tow FT cut Average STDEV Example mg/mm (FT) mg/mm length mm % % Comp. Ex 1-1 13 2.1 10 9.1 1.1 Comp. Ex 1-2 13 2.2 10 7.3 1.0 Ex. 1-1 10 3.0 10 2.7 1.5 Ex. 1-2 8 3.5 10 1.9 1.4 Comp. Ex 1-3 13 2.1 20 9.1 1.4 Comp. Ex 1-4 13 2.2 20 9.6 1.7 Ex. 1-3 10 3.0 20 2.7 1.4 Ex. 1-4 8 3.5 20 2.4 0.8

Selected values from Table 1 are shown in FIG. 1, wherein the x-axis represents the ratio of the volume fraction of charcoal ϕ_(C) divided by the volume fraction of fibres ϕ_(F), and the y-axis represents the charcoal loss L_(C). Examples with a fibre length of 10 mm are represented with an empty circle, whereas examples with a fibre length of 20 mm are represented with a rhombus. As can be seen, a significant reduction in charcoal loss was observed when keeping the ratio ϕ_(C)/ϕ_(F) below a certain value, e.g. less than about 1000% if the charcoal loss is to be limited to about 5% or less, based on the total weight of the charcoal.

When comparing the results represented in FIG. 1, it was observed that shortening fibre length has a slight influence in additive loss reduction. It is expected that by further reducing fibre length, e.g. to 5 mm, additive loss will be limited to about 5% or less by keeping the ratio ϕ_(C)/ϕ_(F) below 1100%.

With the present filter, a significant reduction in additive(s) can be achieved, resulting in cigarettes with improved pressure drop and a manufacturing process that requires less cleaning due to such losses. 

1. A filter for a smoking article comprising randomly oriented discrete fibres and at least one particulate additive, the at least one particulate additive being dispersed within the filter, wherein a value obtained by dividing a volume fraction of the at least one particulate additive by a volume fraction of the fibres is less than about 1100%.
 2. The filter according to claim 1, wherein a range of a combined loading amount of the at least one particulate additive and the fibres is between 2.4 mg/mm and 19 mg/mm.
 3. The filter according to claim 2, wherein the range of the combined loading amount of the at least one particulate additive and the fibres is 11 mg/mm to 13 mg/mm.
 4. The filter according to claim 1, wherein the at least one particulate additive is provided in an amount of between 1 mg/mm and 13.5 mg/mm.
 5. The filter according to claim 4, wherein the amount of the at least one particulate additive is in the range of from 8 mg/mm up to 10 mg/mm.
 6. The filter according to claim 1, wherein the fibres are provided in an amount of between 1.4 mg/mm and 5.5 mg/mm.
 7. The filter according to claim 6, wherein the amount of fibres is in the range of from 3.0 mg/mm up to 3.5 mg/mm.
 8. The filter according to claim 1, wherein the at least one particulate additive comprises or is charcoal.
 9. The filter according to claim 1, wherein the fibres have a filament denier in the range of from 3.0 D to 12.0 D.
 10. The filter according to claim 1, wherein the filter has a cylindrical shape with a circumference of the cylinder being equal to or smaller than 26 mm.
 11. A smoking article comprising a filter according to claim
 1. 12. A method of producing a filter for a smoking article, comprising: adding randomly oriented fibres and at least one particulate additive to the filter, wherein the at least one particulate additive is dispersed in the filter, wherein a value obtained by dividing a volume fraction of the at least one particulate additive by a volume fraction of the fibres is less than about 1100%. 